A high temperature resistant geopolymer based on silica ash modified by alkali activator and its preparation method

Abstract

The application discloses a silica-fume-based alkali activator modified high-temperature-resistant geopolymer and a preparation method thereof, and belongs to the technical field of building materials. The geopolymer comprises the following raw materials in parts by weight: 1200 parts of metakaolin, 2800 parts of fly ash, 891-1485 parts of potassium water glass solution, 0-561 parts of a silica-fume-based alkali activator solution and 354-388 parts of water. In the preparation process of the geopolymer, the silica-fume-based alkali activator is partially used to replace the potassium water glass solution to prepare the high-temperature-resistant geopolymer, so that the mechanical properties and high-temperature resistance of the geopolymer can be improved, meanwhile, the production energy consumption can be effectively reduced, the cost can be saved, and the green performance and environmental protection performance of the geopolymer are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to a silica ash-based alkali activator modified high-temperature-resistant geopolymer and a preparation method thereof. BACKGROUND

[0002] In recent years, with the continuous enhancement of the global awareness of ecological environment protection, green environmental protection and energy saving and carbon reduction have become the new development trend and urgent demand of the construction industry. Under this background, many researchers are committed to exploring new building materials that meet the requirements of green low carbon to improve the high energy consumption and high carbon emission status of the traditional construction industry. In 1978, Davidovits developed a new type of cementing material called "geopolymer" (hereinafter referred to as geopolymer). The material usually takes silica-alumina materials such as metakaolin (MK), fly ash (FA) and slag (GGBS) as precursors, and through the action of an alkaline activator, it undergoes a "dissolution-monomer reconstruction-polycondensation" process, and finally forms a geopolymer with a three-dimensional network structure formed by [SiO4] tetrahedron and [AlO4] tetrahedron interlaced and jointed. With the wide application of geopolymer materials and the continuous deepening of related research, it has shown many excellent performances, such as fast hardening and early strength, high compressive strength, high temperature resistance, strong corrosion resistance, excellent impermeability, etc. Because its raw materials and production process can significantly reduce CO2 emissions, it is considered to be one of the most promising new green cementitious materials in the 21st century.

[0003] With the continuous advancement of urbanization, building fires occur from time to time, posing a serious threat to human life, and building fires must be taken seriously. Recent studies have shown that geopolymer, as a substitute for traditional Portland cement, performs well in fire resistance, providing the possibility of significantly improving the fire resistance of building materials. At present, most studies choose fly ash, slag and metakaolin as single precursor materials to prepare geopolymer. Among them, fly ash-based geopolymer has the best thermal stability at high temperature. However, geopolymer prepared by using a single precursor material often has difficulty in balancing the mechanical properties at room temperature and the high-temperature resistance. For example, fly ash, slag and metakaolin-based geopolymer respectively has the advantages of small high-temperature damage, high strength, and sufficient sintering of viscous at high temperature, but they also have the disadvantages of difficult solidification and low strength, decomposition of hydration products at high temperature, and high pore pressure at high temperature. In addition, compared with strong alkali activation, the use of water glass can usually produce geopolymer with higher strength and relatively dense microstructure. However, as the most commonly used alkaline activator, the high carbon emissions and high price of commercially available water glass solution and the complex preparation process also hinder the popularization and application of geopolymer to some extent. The silica ash-based alkali activator prepared from alkali solution and silica ash has the advantages of low cost, low carbon emission and improved mechanical properties of geopolymer, and has the potential to become a new choice for geopolymer alkali activator. At present, most studies focus on the alkali activation of precursors by strong alkali or water glass solution as alkali activator, while there are few studies on the performance of geopolymer doped with energy-saving, low-cost and simple preparation process of silica ash-based alkali activator as composite alkali activator. Therefore, in order to reduce energy consumption and contribute to green and low carbon, it is very important to study the mechanical properties at room temperature and high-temperature residual mechanical properties of geopolymer modified by silica ash-based alkali activator to prepare high-temperature resistant geopolymer, and to provide ideas and guidance for improving the fire resistance of building materials and promoting the application of geopolymer in practical engineering background. SUMMARY

[0004] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application aims to propose a silica ash-based alkali activator modified high-temperature resistant geopolymer and a preparation method thereof, which dopes silica ash-based alkali activator to replace part of the potassium water glass solution to prepare high-temperature resistant geopolymer in the preparation process of geopolymer, which can not only improve the mechanical properties and high-temperature resistance of geopolymer, but also effectively reduce the production energy consumption, save cost, and improve the green performance and environmental protection performance of geopolymer.

[0005] To achieve the above-mentioned purpose, the present application realizes the following technical scheme:

[0006] A high-temperature resistant geopolymer modified by a silica-fume-based alkali activator, the geopolymer comprises the following raw materials in parts by weight: metakaolin 1200 parts, fly ash 2800 parts, potassium water glass solution 891-1485 parts, silica-fume-based alkali activator solution 0-561 parts, and water 354-388 parts.

[0007] Preferably, the geopolymer comprises the following raw materials in parts by weight: metakaolin 1200 parts, fly ash 2800 parts, potassium water glass solution 1040-1188 parts, silica-fume-based alkali activator solution 280-421 parts, and water 371-380 parts.

[0008] Further preferably, the potassium water glass solution is 1188 parts, the silica-fume-based alkali activator solution is 280 parts, and the water is 371 parts.

[0009] Preferably, the initial modulus of the potassium water glass is 3.1-3.4, and the target modulus is 1.0. Further preferably, the initial modulus of the potassium water glass is 3.3.

[0010] Preferably, the silica-fume-based alkali activator solution is prepared by mixing a potassium hydroxide solution with silica fume at a mass ratio of (3-4):1, and the concentration of the potassium hydroxide solution is 40-60%. Further preferably, the mass ratio of the potassium hydroxide solution to silica fume is 11:3, and the concentration of the potassium hydroxide solution is 50%.

[0011] A preparation method of a high-temperature resistant geopolymer modified by a silica-fume-based alkali activator, comprising the following steps:

[0012] (1) preparing a potassium water glass solution and a silica-fume-based alkali activator solution;

[0013] (2) weighing metakaolin, fly ash, the potassium water glass solution, the silica-fume-based alkali activator solution, and water according to the mixing ratio and placing them for standby use;

[0014] (3) adding the metakaolin and fly ash into a stirring pot together, adjusting the stirring speed to low for 1-2 min, then slowly adding the potassium water glass solution and the silica-fume-based alkali activator solution, adjusting the stirring speed of the stirring machine to medium for preliminary stirring for 0.5 min, then slowly adding the mixing water in multiple times, adjusting the stirring speed to high for 5-10 min, to obtain a mixture;

[0015] (4) pouring the test piece, and after demolding, standard curing is performed to obtain the geopolymer of the present application.

[0016] Preferably, in the step (1), the preparation method of the potassium water glass solution is: first adding solid potassium hydroxide particles into potassium water glass with an initial modulus of 3.3, slowly adding multiple times while continuously stirring, and after standing at room temperature for 24 h, obtaining a potassium water glass solution with a modulus of 1.0.

[0017] Preferably, in the step (1), the preparation method of the silica fume-based alkali activator solution is: adding silica fume powder into potassium hydroxide solution, slowly adding multiple times and constantly stirring, and then standing at room temperature for 24 hours to obtain the silica fume-based alkali activator solution.

[0018] Preferably, in the step (3), the low-speed rotation speed is 100-110 r / min, the medium-speed rotation speed is 180-190 r / min, and the high-speed rotation speed is 400-410 r / min. Further preferably, the low-speed rotation speed is 108 r / min, the medium-speed rotation speed is 188 r / min, and the high-speed rotation speed is 403 r / min.

[0019] Compared with the prior art, the technical scheme provided by the present application has the following advantages and beneficial effects:

[0020] (1) The silica fume-based alkali activator modified high-temperature-resistant geopolymer prepared by the present application has excellent mechanical properties and high-temperature resistance, and the compressive strength at room temperature can reach 45.4 MPa, and the compressive strength after 800℃ high-temperature treatment can reach 47.4 MPa. Compared with the geopolymer using potassium water glass solution as the alkali activator, the mechanical properties at room temperature and the residual mechanical properties after high-temperature treatment are both improved to a certain extent.

[0021] (2) The present application uses silica fume-based alkali activator to partially replace potassium water glass solution as a composite alkali activator for modifying geopolymer, which not only can reduce energy consumption, reduce carbon emissions, improve the green performance and environmental protection performance of geopolymer, and contribute to environmental protection, but also can further improve the mechanical properties and high-temperature resistance of geopolymer. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The figure is a comparison chart of geopolymer mechanical properties at room temperature under different replacement rates of silica fume-based alkali activator in the composite alkali activator.

[0023] Figure 2 The figure is a comparison chart of geopolymer residual mechanical properties after 800℃ under different replacement rates of silica fume-based alkali activator in the composite alkali activator.

[0024] Figure 3 The figure is a comparison chart of geopolymer mechanical properties at room temperature and residual mechanical properties after high-temperature treatment of the comparative examples 1-5 and the examples 1-2. DETAILED DESCRIPTION

[0025] In order to make those skilled in the art better understand the technical scheme of the present application, the preferred embodiments of the present application are described below in combination with specific examples, but it should not be understood as a limitation of the present application, but only as an example.

[0026] The test methods or test methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are obtained from conventional commercial channels or prepared by conventional methods unless otherwise specified.

[0027] Example 1:

[0028] In this example, the replacement rate of silica ash-based alkali activator in the composite alkali activator is 20%.

[0029] The main materials include, in parts by weight: metakaolin 1200 parts, fly ash 2800 parts, potassium water glass solution 1188 parts, silica ash-based alkali activator solution (silica ash, potassium hydroxide solution) 280 parts, and water 371 parts.

[0030] The initial modulus of the potassium water glass is 3.3, and the target modulus is 1.0. The mass ratio of potassium hydroxide solution to silica ash is 11:3, and the concentration of potassium hydroxide solution is 50%.

[0031] The preparation method of the geopolymer is:

[0032] (1) First, add solid potassium hydroxide particles to potassium water glass with an initial modulus of 3.3, and slowly add multiple times while continuously stirring. After standing at room temperature for 24 hours, a potassium water glass solution with a modulus of 1.0 is obtained. Add silica ash powder to the potassium hydroxide solution, slowly add multiple times while continuously stirring, and after standing at room temperature for 24 hours, a silica ash-based alkali activator solution is obtained;

[0033] (2) Weigh the metakaolin, fly ash, potassium water glass solution, silica ash-based alkali activator solution, and water according to the mixing ratio and place them aside for use;

[0034] (3) Add metakaolin and fly ash together into a stirring pot, adjust to low speed 108 r / min, and stir for 1-2 min. After the powder is evenly mixed, slowly add the potassium water glass solution and the silica ash-based alkali activator solution. Adjust the stirrer to medium speed 188 r / min, and after preliminary stirring for 0.5 min, slowly add the mixing water in multiple times. Adjust to high speed 403 r / min, and stir for 5-10 min to obtain the mixture;

[0035] (4) Pour the test piece, demold, and standard cure to obtain the geopolymer of the present application.

[0036] The silica ash-based alkali activator modified high temperature resistant geopolymer is poured and cured at room temperature for 1 day, then demolded and placed in a standard curing room for 28 days to the test age. The test piece size of the silica ash-based alkali activator modified high temperature resistant geopolymer before and after high temperature is 40mm*40mm*40mm.

[0037] The high temperature exposure test uses a box muffle furnace, and the test is divided into four target temperatures: 200℃, 400℃, 600℃, and 800℃. After the test block is cured for 28 days, it is placed in the furnace, heated to the target temperature at a rate of 10℃ / min, and then kept at the target temperature for 1 hour. After the furnace is turned off and the exhaust hole is opened, the test block is taken out after it cools to room temperature, and the subsequent corresponding mechanical properties are tested.

[0038] The mechanical property test results are as follows:

[0039] The compressive strength of the geopolymer at room temperature is 45.4MPa.

[0040] The residual compressive strength of the geopolymer after 200℃ is 61.7MPa.

[0041] The residual compressive strength of the geopolymer after 400℃ is 53.8MPa.

[0042] The residual compressive strength of the geopolymer after 600℃ is 58.2MPa.

[0043] The residual compressive strength of the geopolymer after 800℃ is 47.4MPa.

[0044] Example 2:

[0045] In this example, the replacement rate of silica ash-based alkali activator in the composite alkali activator is 30%.

[0046] The main materials include, by weight: metakaolin 1200 parts, fly ash 2800 parts, potassium water glass solution 1040 parts, silica ash-based alkali activator solution (silica ash, potassium hydroxide solution) 421 parts, and water 380 parts.

[0047] The initial modulus of the potassium water glass is 3.3, and the target modulus is 1.0. The mass ratio of potassium hydroxide solution to silica ash is 11:3, and the concentration of potassium hydroxide solution is 50%.

[0048] The preparation method of the geopolymer is:

[0049] (1) First, solid potassium hydroxide particles are added to potassium water glass with an initial modulus of 3.3, and multiple slow additions are made with constant stirring. After standing at room temperature for 24 hours, a potassium water glass solution with a modulus of 1.0 is obtained. Silica ash powder is added to the potassium hydroxide solution, and multiple slow additions are made with constant stirring. After standing at room temperature for 24 hours, a silica ash-based alkali activator solution is obtained;

[0050] (2) The metakaolin, fly ash, potassium water glass solution, silica ash-based alkali activator solution, and water are weighed according to the mixing ratio and placed for standby use;

[0051] (3) the metakaolin and fly ash are added into a stirring pot, and the stirring speed is adjusted to 108 r / min, and the powder is stirred for 1-2 min, then the potassium water glass solution and the silica ash-based alkali activator solution are slowly added, the stirring speed is adjusted to 188 r / min, and the mixture is preliminarily stirred for 0.5 min, then the mixing water is slowly added in multiple times, the stirring speed is adjusted to 403 r / min, and the mixture is stirred for 5-10 min to obtain a mixture;

[0052] (4) the test piece is poured, and the geopolymer of the application is obtained after demolding and standard curing.

[0053] After the high-temperature resistant geopolymer modified by the silica ash-based alkali activator is poured and cured at room temperature for 1 day, the test piece is removed and placed in a standard curing room for curing for 28 d to a test age. The test piece size for testing the compressive strength of the high-temperature resistant geopolymer modified by the silica ash-based alkali activator before and after high temperature is 40 mm*40 mm*40 mm.

[0054] The high-temperature exposure test uses a box-type muffle furnace, and the test is divided into four target temperatures: 200℃, 400℃, 600℃ and 800℃. After the test block is cured for 28 d, it is placed in the furnace, heated to the target temperature at a rate of 10℃ / min, and then kept at the target temperature for 1 h. After the furnace is turned off and the exhaust hole is opened, the test block is removed when it cools to room temperature, and the subsequent corresponding mechanical properties are tested.

[0055] The mechanical property test results are as follows:

[0056] The compressive strength of the geopolymer at room temperature is 37.7 MPa.

[0057] The residual compressive strength of the geopolymer after 200℃ is 55.7 MPa.

[0058] The residual compressive strength of the geopolymer after 400℃ is 51.7 MPa.

[0059] The residual compressive strength of the geopolymer after 600℃ is 56.7 MPa.

[0060] The residual compressive strength of the geopolymer after 800℃ is 42.5 MPa.

[0061] Comparative Example 1:

[0062] In this example, potassium water glass is used as a single alkali activator.

[0063] The main materials include, by weight, 1200 parts of metakaolin, 2800 parts of fly ash, 1485 parts of potassium water glass solution and 354 parts of water. The initial modulus of the potassium water glass is 3.3, and the target modulus is 1.0.

[0064] The preparation method of the geopolymer is as follows:

[0065] (1) first, solid potassium hydroxide is added to the initial modulus of 3.3 potassium water glass, slowly added multiple times and constantly stirred, after standing at room temperature for 24h, the modulus of the potassium water glass is 1.0;

[0066] (2) the metakaolin, fly ash, potassium water glass solution and water are weighed according to the mixing ratio and placed for standby use;

[0067] (3) the metakaolin and fly ash are added to a stirring pot, adjusted to low speed 108r / min, and stirred for 1-2min, after the powder is uniformly mixed, the potassium water glass solution is slowly added, the stirrer is adjusted to medium speed 188r / min, and after preliminary stirring for 0.5min, the mixing water is slowly added in multiple times, adjusted to high speed 403r / min, and stirred for 5-10min to obtain a mixture;

[0068] (4) pouring the test piece, after demolding, the standard curing is carried out to obtain the geopolymer of the application.

[0069] The silica ash-based alkali activator modified high-temperature resistant geopolymer is poured, cured at room temperature for 1 day, demolded and placed in a standard curing room for curing for 28d to a test age. The high-temperature resistant geopolymer before and after high temperature has a compressive strength test piece size of 40mm*40mm*40mm.

[0070] The high-temperature exposure test uses a box-type muffle furnace, and the test is divided into four target temperatures: 200℃, 400℃, 600℃ and 800℃. After curing for 28d, the test block is taken out, placed in the furnace, heated to the target temperature at a heating rate of 10℃ / min, and then kept at the target temperature for 1h. After the furnace is turned off and the exhaust hole is opened, the test block is taken out after cooling to room temperature, and the subsequent corresponding mechanical properties are tested.

[0071] The mechanical property test results are as follows:

[0072] The compressive strength of the geopolymer at room temperature is 32.5MPa.

[0073] The residual compressive strength of the geopolymer after 200℃ is 47.8MPa.

[0074] The residual compressive strength of the geopolymer after 400℃ is 39.2MPa.

[0075] The residual compressive strength of the geopolymer after 600℃ is 35.0MPa.

[0076] The residual compressive strength of the geopolymer after 800℃ is 37.1MPa.

[0077] Comparative example 2:

[0078] In this example, the replacement rate of silica ash-based alkali activator in the composite alkali activator is 5%.

[0079] The main materials include, by weight parts, metakaolin 1200 parts, fly ash 2800 parts, potassium water glass solution 1411 parts, silica ash-based alkali activator solution (silica ash, potassium hydroxide solution) 70 parts, and water 359 parts.

[0080] The initial modulus of the potassium water glass is 3.3, and the target modulus is 1.0. The mass ratio of the potassium hydroxide solution to the silica ash is 11:3, and the concentration of the potassium hydroxide solution is 50%.

[0081] The preparation method of the geopolymer is as follows:

[0082] (1) First, solid potassium hydroxide particles are added to potassium water glass with an initial modulus of 3.3, and multiple slow additions are made while continuously stirring. After standing at room temperature for 24 hours, a potassium water glass solution with a modulus of 1.0 is obtained. Silica ash powder is added to the potassium hydroxide solution, and multiple slow additions are made while continuously stirring. After standing at room temperature for 24 hours, a silica ash-based alkali activator solution is obtained;

[0083] (2) The metakaolin, fly ash, potassium water glass solution, silica ash-based alkali activator solution, and water are weighed according to the mixing ratio and placed for standby use;

[0084] (3) The metakaolin and fly ash are added together into a stirring pot, and the stirring speed is adjusted to 100 r / min. After the powder mixture is uniformly mixed, the potassium water glass solution and the silica ash-based alkali activator solution are slowly added. The stirring speed is adjusted to 180 r / min, and the mixture is preliminarily stirred for 0.5 min. Then, the water is slowly added in multiple portions, and the stirring speed is adjusted to 400 r / min. After stirring for 5-10 min, a mixture is obtained;

[0085] (4) The test piece is poured and cured, and after demolding, the standard curing is performed to obtain the geopolymer of the present application.

[0086] After the silica ash-based alkali activator modified high-temperature resistant geopolymer is poured and cured at room temperature for 1 day, it is removed from the mold and placed in a standard curing room for curing for 28 days to the test age. The test piece size for testing the compressive strength of the silica ash-based alkali activator modified high-temperature resistant geopolymer before and after high temperature is 40 mm*40 mm*40 mm.

[0087] The high-temperature exposure test uses a box-type muffle furnace. The test is divided into four target temperatures: 200℃, 400℃, 600℃, and 800℃. After the test block is cured for 28 days, it is placed in the furnace and heated to the target temperature at a rate of 10℃ / min. After maintaining the target temperature for 1 hour, the electric furnace is turned off and the exhaust hole is opened. After the test block cools to room temperature, it is removed for subsequent mechanical performance testing.

[0088] The mechanical performance test results are as follows:

[0089] The geopolymer has a compressive strength of 38.2 MPa at room temperature.

[0090] The geopolymer has a residual compressive strength of 48.5 MPa after 200℃.

[0091] The geopolymer has a residual compressive strength of 44.4 MPa after 400℃.

[0092] The geopolymer has a residual compressive strength of 43.6 MPa after 600℃.

[0093] The geopolymer has a residual compressive strength of 34.6 MPa after 800℃.

[0094] Comparative Example 3:

[0095] In this example, the replacement rate of silica ash-based alkali activator in the composite alkali activator is 10%.

[0096] The main materials include, by weight, 1200 parts of metakaolin, 2800 parts of fly ash, 1337 parts of potassium water glass solution, 140 parts of silica ash-based alkali activator solution (silica ash, potassium hydroxide solution), and 363 parts of water.

[0097] The initial modulus of the potassium water glass is 3.3, and the target modulus is 1.0. The mass ratio of the potassium hydroxide solution to the silica ash is 11:3, and the concentration of the potassium hydroxide solution is 50%.

[0098] The preparation method of the geopolymer is as follows:

[0099] (1) First, solid potassium hydroxide particles are added to potassium water glass with an initial modulus of 3.3, and multiple slow additions are made with constant stirring. After standing at room temperature for 24 hours, a potassium water glass solution with a modulus of 1.0 is obtained. Silica ash powder is added to the potassium hydroxide solution, and multiple slow additions are made with constant stirring. After standing at room temperature for 24 hours, a silica ash-based alkali activator solution is obtained;

[0100] (2) The metakaolin, fly ash, potassium water glass solution, silica ash-based alkali activator solution, and water are weighed according to the mixing ratio and placed for standby;

[0101] (3) The metakaolin and fly ash are added together into a stirring pot, and the stirring speed is adjusted to 110 r / min. After the powder mixture is uniformly mixed, the potassium water glass solution and the silica ash-based alkali activator solution are slowly added. The stirring machine is adjusted to a medium speed of 190 r / min, and after preliminary stirring for 0.5 min, the water is slowly added in multiple portions. The stirring speed is adjusted to 410 r / min, and stirring is performed for 5-10 min to obtain a mixture;

[0102] (4) The test piece is poured and demolded, and standard curing is performed to obtain the geopolymer of the present application.

[0103] The high-temperature resistant geopolymer modified by the silica ash-based alkali activator is poured and cured at room temperature for 1 day, then removed from the mold and placed in a standard curing chamber for curing for 28 days to a test age; the size of the test specimen for testing the compressive strength of the high-temperature resistant geopolymer before and after high-temperature exposure is 40 mm*40 mm*40 mm.

[0104] The high-temperature exposure test uses a box-type muffle furnace, and the test is divided into four target temperatures: 200℃, 400℃, 600℃, and 800℃. The test block is removed after curing for 28 days, placed in the furnace, and heated to the target temperature at a heating rate of 10℃ / min, and then kept at the target temperature for 1 hour. After the furnace is turned off and the exhaust hole is opened, the test block is removed after cooling to room temperature, and the subsequent corresponding mechanical properties are tested.

[0105] The mechanical property test results are as follows:

[0106] The compressive strength of the geopolymer at room temperature is 61.2 MPa.

[0107] The residual compressive strength of the geopolymer after 200℃ is 59.8 MPa.

[0108] The residual compressive strength of the geopolymer after 400℃ is 45.9 MPa.

[0109] The residual compressive strength of the geopolymer after 600℃ is 43.1 MPa.

[0110] The residual compressive strength of the geopolymer after 800℃ is 33.4 MPa.

[0111] Comparative Example 4:

[0112] In this example, the replacement rate of the silica ash-based alkali activator in the composite alkali activator is 15%.

[0113] The main materials include, by weight fraction: 1200 parts of metakaolin, 2800 parts of fly ash, 1262 parts of potassium water glass solution, 210 parts of silica ash-based alkali activator solution (silica ash, potassium hydroxide solution), and 367 parts of water.

[0114] The initial modulus of the potassium water glass is 3.3, and the target modulus is 1.0. The mass ratio of the potassium hydroxide solution to silica ash is 11:3, and the concentration of the potassium hydroxide solution is 50%.

[0115] The preparation method of the geopolymer is as follows:

[0116] (1) First, solid potassium hydroxide particles are added to potassium water glass with an initial modulus of 3.3, and multiple slow additions are made with constant stirring. After standing at room temperature for 24 hours, a potassium water glass solution with a modulus of 1.0 is obtained. Silica ash powder is added to the potassium hydroxide solution, and multiple slow additions are made with constant stirring. After standing at room temperature for 24 hours, a silica ash-based alkali activator solution is obtained.

[0117] (2) Take metakaolin, fly ash, potassium water glass solution, silica ash-based alkali activator solution and water by mixing ratio, and place for standby;

[0118] (3) Put metakaolin and fly ash into a stirring pot together, adjust to low speed 109 r / min, stir for 1-2 min, after the powder is uniformly mixed, slowly add potassium water glass solution and silica ash-based alkali activator solution, adjust the stirring machine to medium speed 185 r / min, after preliminary stirring for 0.5 min, slowly add mixing water in multiple times, adjust to high speed 405 r / min, stir for 5-10 min, to obtain a mixture;

[0119] (4) Pour the test piece, after demolding, standard curing is obtained, and the geopolymer of the application is obtained.

[0120] The silica ash-based alkali activator modified high-temperature resistant geopolymer is cured at room temperature for 1 day after pouring, then demolded and placed in a standard curing room for curing for 28 d to a test age. The high-temperature resistant geopolymer before and after high temperature has a compressive strength test piece size of 40 mm*40 mm*40 mm.

[0121] The high-temperature exposure test uses a box-type muffle furnace, and the test is divided into four target temperatures: 200℃, 400℃, 600℃, and 800℃. After curing for 28 d, the test block is taken out and placed in the furnace, heated to the target temperature at a rate of 10℃ / min, and then kept at the target temperature for 1 h. After closing the electric furnace and opening the exhaust hole, the test block is taken out after cooling to room temperature, and the subsequent corresponding mechanical properties are tested.

[0122] The mechanical property test results are as follows:

[0123] The compressive strength of the geopolymer at room temperature is 49.4 MPa.

[0124] The residual compressive strength of the geopolymer after 200℃ is 60.3 MPa.

[0125] The residual compressive strength of the geopolymer after 400℃ is 47.8 MPa.

[0126] The residual compressive strength of the geopolymer after 600℃ is 44.5 MPa.

[0127] The residual compressive strength of the geopolymer after 800℃ is 33.2 MPa.

[0128] Comparative Example 5:

[0129] In this example, the replacement rate of silica ash-based alkali activator in the composite alkali activator is 40%.

[0130] The main materials include the following in parts by weight: metakaolin 1200 parts, fly ash 2800 parts, potassium water glass solution 891 parts, silica ash-based alkali activator solution (silica ash, potassium hydroxide solution) 561 parts, and water 388 parts.

[0131] The initial modulus of the potassium water glass is 3.3, and the target modulus is 1.0. The mass ratio of the potassium hydroxide solution to the silica ash is 11:3, and the concentration of the potassium hydroxide solution is 50%.

[0132] The preparation method of the geopolymer is as follows:

[0133] (1) First, solid potassium hydroxide particles are added to potassium water glass with an initial modulus of 3.3, and multiple slow additions are made while continuously stirring. After standing at room temperature for 24 hours, a potassium water glass solution with a modulus of 1.0 is obtained. Silica ash powder is added to the potassium hydroxide solution, and multiple slow additions are made while continuously stirring. After standing at room temperature for 24 hours, a silica ash-based alkali activator solution is obtained;

[0134] (2) The metakaolin, fly ash, potassium water glass solution, silica ash-based alkali activator solution, and water are weighed according to the mixing ratio and placed for standby use;

[0135] (3) The metakaolin and fly ash are added together into a stirring pot, and the stirring speed is adjusted to 105 r / min. After the powder mixture is uniformly mixed, the potassium water glass solution and the silica ash-based alkali activator solution are slowly added. The stirring speed is adjusted to 183 r / min, and the mixture is preliminarily stirred for 0.5 min. Then, the water is slowly added in multiple portions, and the stirring speed is adjusted to 405 r / min. After stirring for 5-10 min, a mixture is obtained;

[0136] (4) The test piece is poured and demolded, and standard curing is performed to obtain the geopolymer of the present application.

[0137] After the silica ash-based alkali activator modified high-temperature resistant geopolymer is poured and cured at room temperature for 1 day, it is removed and placed in a standard curing room for curing for 28 days to the test age. The test piece size for testing the compressive strength of the silica ash-based alkali activator modified high-temperature resistant geopolymer before and after high temperature is 40 mm * 40 mm * 40 mm.

[0138] The high-temperature exposure test uses a box-type muffle furnace. The test is divided into four target temperatures: 200℃, 400℃, 600℃, and 800℃. After the test block is cured for 28 days, it is placed in the furnace and heated to the target temperature at a rate of 10℃ / min. After maintaining the target temperature for 1 hour, the electric furnace is turned off and the exhaust hole is opened. After the test block cools to room temperature, it is removed for subsequent mechanical performance testing.

[0139] The mechanical performance test results are as follows:

[0140] The compressive strength of the geopolymer at room temperature is 30.9 MPa.

[0141] The residual compressive strength of the geopolymer after 400°C is 46.3 MPa.

[0142] The residual compressive strength of the geopolymer after 400°C is 46.3 MPa.

[0143] The residual compressive strength of the geopolymer after 600°C is 46.4 MPa.

[0144] The residual compressive strength of the geopolymer after 800°C is 38.6 MPa.

[0145] Figure 1 The figure is a comparison of the room temperature mechanical properties of the geopolymer with different replacement rates of silica ash-based alkali activator in the composite alkali activator. From Figure 1 It can be seen from the figure that as the replacement rate of silica ash-based alkali activator in the alkali activator gradually increases, the room temperature mechanical properties first increase and then decrease. When the replacement rate of silica ash-based alkali activator is 5%, 10% or 15%, although the room temperature compressive strength is improved, the residual compressive strength after high temperature decreases seriously, and the room temperature mechanical properties and the residual mechanical properties after high temperature cannot be considered together, so a proper amount of silica ash-based alkali activator can be added to modify the geopolymer and enhance the room temperature mechanical properties.

[0146] Figure 2 The figure is a comparison of the residual mechanical properties of the geopolymer after 800°C with different replacement rates of silica ash-based alkali activator in the composite alkali activator. From Figure 2 It can be seen from the figure that as the replacement rate of silica ash-based alkali activator in the alkali activator gradually increases, compared with potassium water glass solution as a single alkali activator, the residual mechanical properties after 800°C are greatly improved when the replacement rate is between 20% and 30%. When the replacement rate of silica ash-based alkali activator is 40%, although the residual compressive strength after high temperature is improved, the room temperature compressive strength decreases slightly, and the room temperature mechanical properties cannot be improved, so a proper amount of silica ash-based alkali activator (replacement rate of 20-30%) can be added to modify the geopolymer and enhance the residual mechanical properties after high temperature, and the room temperature mechanical properties are also considered.

[0147] Figure 3 The figure is a comparison of the room temperature mechanical properties and the residual mechanical properties after high temperature of Comparative Examples 1-5 and Examples 1-2. From Figure 3 It can be seen from the figure that when the replacement rates of silica ash-based alkali activator in Example 1 and Example 2 are 20% and 30% respectively, the room temperature mechanical properties and the residual mechanical properties after high temperature of the geopolymer can be well considered.

[0148] The above merely describes the preferred embodiments of the present application, and it should be pointed out that the above preferred embodiments should not be regarded as a limitation to the present application, and the protection scope of the present application should be defined by the scope of the claims. For those skilled in the art, several improvements and refinements can be made without departing from the spirit and scope of the present application, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A silica-fume-based alkali-activator-modified high-temperature resistant geopolymer, characterized in that, The geopolymer comprises the following raw materials in parts by weight: metakaolin 1200 parts, fly ash 2800 parts, potassium water glass solution 1040-1188 parts, silica ash-based alkali activator solution 280-421 parts, and water 371-380 parts; the silica ash-based alkali activator solution is prepared by mixing potassium hydroxide solution and silica ash at a mass ratio of (3-4):1, and the concentration of the potassium hydroxide solution is 40-60%.

2. The silica-fume-based alkali-activator-modified high-temperature-resistant geopolymer according to claim 1, characterized in that, The potassium water glass solution is 1188 parts, the silica ash-based alkali activator solution is 280 parts, and the water is 371 parts.

3. The silica-fume-based alkali-activator-modified high-temperature resistant geopolymer according to claim 1, characterized in that, The initial modulus of the potassium water glass is 3.1-3.4, and the target modulus is 1.

0.

4. The silica-fume-based alkali-activator-modified high-temperature resistant geopolymer of claim 1, wherein, The mass ratio of the potassium hydroxide solution to silica ash is 11:3, and the concentration of the potassium hydroxide solution is 50%.

5. A method for the production of a silica-fume-based alkali-activated modified refractory geopolymer according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: (1) preparing a potassium water glass solution and a silica ash-based alkali activator solution; (2) weighing metakaolin, fly ash, potassium water glass solution, silica ash-based alkali activator solution, and water according to the mixing ratio and placing them for standby use; (3) adding metakaolin and fly ash together into a stirring pot, adjusting the stirring speed to low for 1-2 min, then slowly adding the potassium water glass solution and the silica ash-based alkali activator solution, adjusting the stirring speed of the stirring machine to medium for preliminary stirring for 0.5 min, then slowly adding water in multiple times, adjusting the stirring speed to high for 5-10 min to obtain a mixture; (4) pouring the test piece, and obtaining the geopolymer after demolding and standard curing.

6. The method of claim 5, wherein the method is characterized by: In step (1), the preparation method of the potassium water glass solution is as follows: first, adding solid potassium hydroxide particles into potassium water glass with an initial modulus of 3.3, slowly adding multiple times and continuously stirring, and then obtaining a potassium water glass solution with a modulus of 1.0 after standing at room temperature for 24 h.

7. The method of claim 5, wherein the method further comprises the step of adding a curing agent to the mixture. In step (1), the preparation method of the silica ash-based alkali activator solution is as follows: adding silica ash powder into a potassium hydroxide solution, slowly adding multiple times and continuously stirring, and then obtaining a silica ash-based alkali activator solution after standing at room temperature for 24 h.

8. The method of claim 5, wherein the method is characterized by: In step (3), the low-speed rotating speed is 100-110 r / min, the medium-speed rotating speed is 180-190 r / min, and the high-speed rotating speed is 400-410 r / min.

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